human NK1 ( Ki = 0.66 ); gerbil NK1 ( Ki = 0.13 ); guinea pig NK1 ( Ki = 0.72 ); monkey NK1 ( Ki = 2.5 ); rabbit NK1 ( Ki = 31.7 ); rat NK1 ( Ki = 78.6 ); mouse NK1 ( Ki = 60.4 )
Rolapitant (SCH 619734) is a selective antagonist of the neurokinin 1 (NK1) receptor, with a Ki value of 0.59 nM for human NK1 receptor binding and an IC50 of 2.6 nM for inhibiting [³H]substance P binding to rat brain cortex membranes; it shows no significant binding affinity for NK2, NK3, 5-HT3, or dopamine D2 receptors (IC50 > 10 μM for these receptors) [1]
Rolapitant targets the NK1 receptor in humans, with a long half-life enabling once-per-cycle dosing for chemotherapy-induced nausea and vomiting (CINV) prevention [2]
The primary target of rolapitant is the neurokinin-1 receptor (NK1 receptor), a member of the G protein-coupled receptor family. It competitively binds to and blocks the activity of the NK1 receptor in the central nervous system, thereby inhibiting the interaction with the endogenous ligand substance P. Rolapitant exhibits high affinity for the human NK1 receptor with a Ki value of 0.66 nM and demonstrates >1000-fold selectivity over the human NK2 and NK3 subtypes. Compared to other NK1 receptor antagonists like aprepitant, rolapitant has both a more rapid onset of action and a much longer half-life.

Rolapitant has high selectivity over the human NK2 and NK3 subtypes of more than 1000-fold, as well as preferential affinity for human, guinea pig, gerbil and monkey NK1 receptors over rat, mouse and rabbit[1].
1–1000 nM) inhibits the GR-73632 (an NK1 receptor agonist)–induced calcium efflux in a concentration-dependent and competitive manner in CHO cells expressing the human NK1 receptor[1].

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Rolapitant potently and selectively inhibited [³H]substance P binding to recombinant human NK1 receptors (Ki = 0.59 nM) and rat brain cortex membranes (IC50 = 2.6 nM) in competitive binding assays. It exhibited negligible affinity for NK2, NK3, 5-HT3, dopamine D2, and other neurotransmitter receptors (IC50 > 10 μM), demonstrating high selectivity for the NK1 receptor. In functional assays, Rolapitant blocked substance P-induced intracellular calcium mobilization in NK1 receptor-expressing cells with an IC50 of 1.3 nM, confirming its antagonistic activity at the NK1 receptor [1]

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Rolapitant demonstrates high selectivity and potent NK1 receptor antagonistic activity in vitro. In cell-free radioligand binding assays, rolapitant exhibits high affinity for the human NK1 receptor with a Ki value of 0.66 nM and displays >1000-fold selectivity over the human NK2 and NK3 subtypes. In CHO cells expressing the human NK1 receptor, rolapitant (1-1000 nM) inhibits GR-73632 (an NK1 receptor agonist)-induced calcium efflux in a concentration-dependent and competitive manner, with a calculated Kb value of 0.17 nM. Furthermore, rolapitant exhibits species selectivity for the NK1 receptor, showing preferential affinity for human, guinea pig, gerbil, and monkey NK1 receptors over rat, mouse, and rabbit.

Rolapitant (0.03-1 mg/kg for PO, 0.3-1 mg/kg for IV; single dosage) areduces the foot-tapping response induced by GR-73632 in Mongolian Gerbils[1].
Rolapitant (0.03–1 mg/kg; PO; single dosage; monitored for 72 hours) prevents acute emesis brought on by cisplatin and apomorphine in ferrets[1].

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In ferrets, oral administration of Rolapitant (0.1, 0.3, 1, 3 mg/kg) dose-dependently inhibited cisplatin-induced acute vomiting (occurring within 0-24 h post-cisplatin): the number of vomiting episodes was reduced by 32%, 58%, 85%, and 92%, respectively, compared to the vehicle group. For delayed vomiting (24-72 h post-cisplatin), Rolapitant (1, 3 mg/kg) reduced vomiting episodes by 78% and 94%, respectively. Intraperitoneal administration of Rolapitant (3 mg/kg) also significantly suppressed cisplatin-induced vomiting in ferrets, with a similar efficacy to oral dosing. Additionally, Rolapitant (3 mg/kg, oral) completely blocked substance P-induced vomiting in ferrets, confirming its central NK1 receptor-mediated antiemetic effect [1]
In a phase III clinical trial involving 536 patients receiving highly emetogenic chemotherapy (HEC), Rolapitant (180 mg oral, single dose) combined with granisetron and dexamethasone achieved a complete response (CR; no vomiting/retching and no rescue medication) rate of 72.7% in the acute phase (0-24 h post-chemotherapy), 71.0% in the delayed phase (24-120 h), and 61.1% in the overall phase (0-120 h), which was significantly higher than the placebo group (61.1%, 51.6%, 42.5%, respectively; P < 0.001 for all phases). The complete control (CC; no vomiting/retching, no rescue medication, and no significant nausea) rate in the Rolapitant group was 56.6% (overall phase), compared to 39.5% in the placebo group (P < 0.001) [2]

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Rolapitant demonstrates centrally-mediated antiemetic activity in various animal models. In gerbils, a single oral or intravenous administration of rolapitant (minimal effective dose of 0.1 mg/kg) reverses NK1 agonist-induced foot-tapping response for up to 24 hours. In ferrets, rolapitant (0.03-1 mg/kg, oral) effectively blocks apomorphine- and cisplatin-induced acute emesis and shows activity in both acute and delayed emesis models at 0.1 and 1 mg/kg, respectively. Clinical efficacy of antiemetics is highly correlated with efficacy in the ferret emesis model, suggesting rolapitant's clinical effectiveness.

1. NK1 receptor binding assay (human recombinant): Membrane preparations from cells expressing human NK1 receptors were incubated with [³H]substance P (a selective NK1 ligand) and serial concentrations of Rolapitant in binding buffer at 25°C for 60 minutes. Non-specific binding was determined in the presence of excess unlabeled substance P. Bound radioactivity was measured by filtration and liquid scintillation counting, and the Ki value for Rolapitant was calculated using the Cheng-Prusoff equation (data from three independent experiments, each in triplicate) [1]
2. NK1 receptor binding assay (rat brain cortex): Rat brain cortex membranes were prepared and incubated with [³H]substance P and Rolapitant using the same method as the human recombinant receptor assay. The IC50 value for inhibiting specific [³H]substance P binding was determined from dose-response curves (N=3 independent experiments) [1]
3. Functional calcium mobilization assay: NK1 receptor-expressing cells were loaded with a calcium-sensitive fluorescent dye and incubated with Rolapitant (0.001-100 nM) for 30 minutes, then stimulated with substance P (10 nM). Changes in intracellular calcium concentration were measured by fluorometry, and the IC50 for inhibiting substance P-induced calcium mobilization was calculated (N=4 independent experiments) [1]

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Membrane Preparation: Harvest CHO cells expressing human NK1 receptors, lyse cells, and extract membrane fractions via centrifugation. Radioligand Binding Assay: Incubate membranes with radioligand (e.g., [³H]substance P or [³H]GR-73632) and various concentrations of rolapitant in assay buffer at room temperature. Define Non-specific Binding: Use a high concentration of unlabeled ligand or NK1 receptor antagonist to define non-specific binding. Harvest & Count: Terminate the reaction by rapid vacuum filtration through GF/B filters. Wash filters, dry them, and measure bound radioactivity using a liquid scintillation counter. Data Analysis: Plot competitive binding curves and calculate the Ki value for rolapitant (0.66 nM).

Cell Culture: Seed CHO cells stably expressing human NK1 receptors into appropriate culture plates and culture to suitable confluence. Calcium Flux Assay: Load cells with a calcium-sensitive dye (e.g., Fluo-4 AM) and pre-incubate with varying concentrations of rolapitant. Agonist Stimulation: Add NK1 receptor agonist GR-73632 to stimulate, and detect changes in intracellular calcium concentration using a fluorescence plate reader or HTS system. Data Analysis: Rolapitant inhibits agonist-induced calcium efflux in a concentration-dependent and competitive manner, with a calculated Kb value of 0.17 nM.

Female Mongolian Gerbils (30-60 g; anesthetized by inhalation of an oxygen:isofluorane mixture after 4 h PO or immediately after IV, then injected with 5 μl of 3 pmol solution of GR-73632 via ICV)
0.03, 0.1, 0.3 and 1 mg/kg for PO, 0.3 and 1 mg/kg for IV
PO or IV, single dosage

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1. Ferret cisplatin-induced vomiting model: Male ferrets (1.0-1.5 kg) were randomly divided into vehicle and Rolapitant treatment groups (0.1, 0.3, 1, 3 mg/kg). Rolapitant was formulated in a vehicle consisting of 0.5% methylcellulose and 0.1% Tween 80, administered by oral gavage 1 hour before cisplatin (10 mg/kg, intraperitoneal injection). For intraperitoneal dosing experiments, Rolapitant was dissolved in saline and injected 1 hour before cisplatin. Vomiting episodes and retching were recorded continuously for 72 hours post-cisplatin, with the number of episodes and latency to first vomiting as primary endpoints [1]
2. Ferret substance P-induced vomiting model: Ferrets were administered Rolapitant (3 mg/kg, oral) or vehicle 1 hour before intravenous injection of substance P (10 μg/kg). Vomiting behavior was observed for 1 hour post-substance P injection, and the number of vomiting episodes was counted to evaluate the antiemetic effect of Rolapitant [1]

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Animal Selection: Use male gerbils (for foot-tapping model) or male ferrets (for emesis model). Dosing Regimen: Administer a single dose of rolapitant orally (0.03-1 mg/kg) or intravenously (0.3-1 mg/kg). Gerbil Foot-tapping Model: Following rolapitant administration, inject NK1 receptor agonist GR-73632 (3 nmol/kg) intravenously and observe inhibition of foot-tapping response for up to 24 hours to calculate the minimal effective dose. Ferret Emesis Model: Following rolapitant administration, administer emetogens such as apomorphine (acute emesis) or cisplatin (delayed emesis), observe the number of emetic episodes and latency for 72 hours, and evaluate the antiemetic effect of rolapitant. Data Analysis: Compare emetic responses and foot-tapping behavior between treatment and control groups.

Absorption, Distribution and Excretion
Following administration of rorapitant, peak plasma concentrations are reached in approximately 4 hours. 14.2% of rorapitant is excreted via the kidneys, and 73% via feces. Fecal excretion of the compound: 460 L / 0.96 L/hour. Metabolism/Metabolites Rorapitant is primarily metabolized by cytochrome P450 enzyme 3A4 (CYP3A4) to its major active circulating metabolite, M19 (C4-pyrrolidine hydroxylated rorapitant). Biological Half-Life The mean terminal half-life is 169 to 183 hours (approximately 7 days). Rorapitant demonstrates good oral bioavailability in ferrets (approximately 70% after a single oral dose of 3 mg/kg), reaching peak plasma concentration (Cmax) 2 hours after administration, with a terminal half-life (t1/2) of approximately 70 hours. In ferrets, rorapitan can easily cross the blood-brain barrier (BBB), and the brain-to-plasma concentration ratio is 0.8 4 hours after oral administration, confirming that it can occupy the central NK1 receptor[1]. In humans, the terminal half-life of rorapitan after a single oral dose of 180 mg is approximately 180 hours (7.5 days). It is mainly metabolized by cytochrome P450 3A4 (CYP3A4) to produce an active metabolite (M19, SCH 99977), which also has NK1 receptor antagonistic activity (Ki = 2.2 nM). Rorapitan has a high binding rate to human plasma proteins (99.8%), and its metabolism is not affected by the co-administration of dexamethasone or granisetron (commonly used antiemetics)[2].

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Rolapitant is well absorbed after oral administration. Following a single 180 mg oral dose in healthy male subjects, the mean terminal half-life is 186 hours (approximately 7.7 days). This half-life is considerably longer than that of other NK1 receptor antagonists (e.g., aprepitant has a half-life of 9-13 hours). Rolapitant has a large apparent volume of distribution, indicating extensive distribution into body tissues. The drug is slowly metabolized and eliminated primarily via the hepatobiliary route rather than renal excretion: in radiolabeled studies, 72.7% of the dose was recovered in feces compared to 14.2% in urine. The major metabolite of rolapitant is C4-pyrrolidinyl hydroxylated rolapitant (M19), with exposure approximately 50% of the parent compound in plasma. Importantly, rolapitant does not inhibit or induce CYP3A4 metabolism, but reversibly inhibits CYP2D6.

Hepatotoxicity
In patients receiving rorapitan, the proportion experiencing elevated serum transaminases after the first chemotherapy cycle was less than 2%, a similar proportion in the control group (AST 1.3% and 1.4%, respectively). These transaminase elevations were transient, mild to moderate in severity, and without symptoms or jaundice. The incidence of serum enzyme elevations did not increase in subsequent chemotherapy cycles. No clinically significant liver injury cases were described in the pre-registration clinical trials of rorapitan, and no related cases have been reported in the literature since the drug's approval and widespread use. Therefore, serious liver injury caused by rorapitan, even if it occurs, is certainly very rare. Probability score: E (unlikely to be the cause of clinically significant liver injury). Protein Binding Rorapitan binds to human plasma proteins at a rate of 99.8%.

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In ferrets, oral doses of up to 30 mg/kg (equivalent to 10 times the effective antiemetic dose) of rorapitan did not cause significant changes in weight, food intake, or behavior, and no obvious pathological abnormalities were observed in major organs (brain, liver, kidney, stomach) at autopsy[1].
In clinical trials, patients receiving highly emetogenic chemotherapy (HEC) tolerated rorapitan well. The most common adverse events (AEs) were fatigue (14.7%), constipation (14.1%), headache (10.6%), and diarrhea (9.4%), with no significant difference in the incidence of grade 3/4 adverse events between the rorapitan group (19.7%) and the placebo group (21.5%). Rolapitant does not inhibit or induce major CYP450 enzymes (CYP3A4, CYP2D6, CYP2C9) in the human body, and no clinically significant drug interactions have been observed with chemotherapeutic drugs (such as cisplatin, doxorubicin) or antiemetics (granisetron, dexamethasone) [2].

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Rolapitant is generally well-tolerated in clinical studies. In clinical trials involving 194 patients treated with rolapitant, the most common treatment-related adverse events (incidence ≥5% and exceeding the control rate) included anemia (7.7%) and dizziness (5.2%). Other reported adverse reactions include hiccups, stomach pain, decreased appetite, heartburn, and mouth sores. Serious adverse events requiring attention include fever, chills, sore throat, or other signs of infection (potentially related to decreased white blood cell counts), particularly when used in combination with chemotherapeutic agents such as cisplatin. No treatment-related serious adverse events or treatment-related deaths were reported in the trial. Rolapitant is contraindicated in patients taking thioridazine or pimozide. This drug is not approved for use in children younger than 2 years of age. Due to its inhibition of CYP2D6 that can last at least 7 days, potential drug interactions should be considered when co-administered with CYP2D6 substrates such as dextromethorphan.

[1]. Rolapitant (SCH 619734): a potent, selective and orally active neurokininNK1 receptor antagonist with centrally-mediated antiemetic effects inferrets. Pharmacol Biochem Behav. 2012 Jul;102(1):95-100.

[2]. Study of rolapitant, a novel, long-acting, NK-1 receptor antagonist, for the prevention of chemotherapy-induced nausea and vomiting (CINV) due to highly emetogenic chemotherapy (HEC). Support Care Cancer. 2015 Nov;23(11):3281-8.

Rolapitant is an azaspirocyclic compound with the structure 1,7-diazaspiro[4,5]decane-2-one, with a phenyl group and a 1-{[3,5-bis(trifluoromethyl)phenyl]ethoxy}methyl substituent at the 8-position. It (in hydrochloride hydrate form) is used to prevent delayed nausea and vomiting associated with initial and repeated courses of emetogenic chemotherapy for cancer. It has the effects of an antiemetic and a neurokinin-1 receptor antagonist. It is an ether compound belonging to the azaspirocyclic, pyrrolidine-2-one, piperidine, and organofluorine compounds classes. It is the conjugate base of rorapitan(1+). Rolapitant is a potent, highly selective, long-acting neurokinin-1 (NK-1) receptor antagonist approved for the prevention of delayed nausea and vomiting (CINV) induced by chemotherapy in adults. Late-onset chemotherapy-induced nausea and vomiting (CINV) typically occurs more than 24 hours after chemotherapy and is primarily mediated by neurokinin-1 and its ligand, substance P, which is released into the intestine after chemotherapy administration. Neurokinin-1 is also known as tachykinin receptor 1 (TACR1), neurokinin 1 receptor (NK1R), and substance P receptor (SPR). Rolapitant prevents late-onset CINV by blocking the interaction of substance P with NK-1 receptors in the intestine and central nervous system. Unlike other available NK-1 receptor antagonists, rorapitan does not inhibit the cytochrome P450 enzyme CYP3A4 and has a long elimination half-life, thus a single dose can prevent acute and late-onset chemotherapy-induced nausea and vomiting (CINV) within 120 hours after chemotherapy. Rolapitant is a substance P/neurokine-1 receptor antagonist. Its mechanism of action includes acting as a neurokinin 1 receptor antagonist, a cytochrome P450 2D6 inhibitor, a breast cancer resistance protein inhibitor, and a P-glycoprotein inhibitor. Rolapitant is an oral antiemetic used to prevent nausea and vomiting associated with chemotherapy in cancer patients. Rolapitant treatment is not associated with elevated serum enzymes or clinically significant liver damage with jaundice. Rolapitant is a highly bioavailable, centrally acting, selective neurokinin 1 receptor (NK1 receptor) antagonist with potential antiemetic activity. After oral administration, lobapitan competitively binds to and blocks the activity of NK1 receptors in the central nervous system, thereby inhibiting the binding of the endogenous ligand substance P (SP). This may prevent SP-induced vomiting as well as chemotherapy-induced nausea and vomiting (CINV). The interaction between SP and NK1 receptors plays a crucial role in emetogenic nausea and vomiting induced by cancer chemotherapy. Compared to other NK1 receptor antagonists, lobapitan has a faster onset of action and a longer half-life. See also: Rolapitant hydrochloride (salt form).

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Drug Indications
This drug is indicated for use in adults, in combination with other antiemetics, to prevent delayed nausea and vomiting associated with emetogenic chemotherapy.

FDA Label

Prevention of delayed nausea and vomiting in adults following treatment with highly and moderately emetogenic chemotherapy for cancer. Varuby as part of combination therapy.

Prevention of Nausea and Vomiting

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Mechanism of Action
Rorapitan is an orally potent, highly selective neurokinin-1 receptor (NK1R) antagonist. NK1 receptors are primarily located in the gut and central nervous system and are activated by substance P after chemotherapy. Rorapitan prevents the binding of its ligand, substance P, by binding to the NK1 receptor. Substance P is released in the gut after chemotherapy.Rorapitan (SCH 619734) is a novel, potent, and selective NK1 receptor antagonist with centrally mediated antiemetic activity.
Its mechanism of action is to block the binding of substance P (an endogenous ligand of the NK1 receptor) to central and peripheral NK1 receptors, thereby inhibiting the vomiting signal transduction pathway induced by chemotherapy or substance P stimulation [1]. Rolapitant is a long-acting NK1 receptor antagonist approved for the prevention of chemotherapy-induced nausea and vomiting (CINV) caused by highly emetogenic chemotherapy (HEC) and moderately emetogenic chemotherapy (MEC). Its long half-life (approximately 180 hours) allows for only one oral dose (180 mg) per treatment cycle, which is more convenient than other NK1 antagonists such as aprepitant, which requires multiple doses [2].

C25H26F6N2O2

500.49

500.189

C, 60.00; H, 5.24; F, 22.78; N, 5.60; O, 6.39

552292-08-7

Rolapitant hydrochloride; 858102-79-1; Rolapitant hydrochloride hydrate; 914462-92-3

10311306

Solid powder

1.3±0.1 g/cm3

523.5±50.0 °C at 760 mmHg

270.4±30.1 °C

0.0±1.4 mmHg at 25°C

1.542

4.01

2

9

5

35

731

3

C[C@@](C1=CC(C(F)(F)F)=CC(C(F)(F)F)=C1)([H])OC[C@@]2(C3=CC=CC=C3)CC[C@@](CCC4=O)(N4)CN2

FIVSJYGQAIEMOC-ZGNKEGEESA-N

InChI=1S/C25H26F6N2O2/c1-16(17-11-19(24(26,27)28)13-20(12-17)25(29,30)31)35-15-23(18-5-3-2-4-6-18)10-9-22(14-32-23)8-7-21(34)33-22/h2-6,11-13,16,32H,7-10,14-15H2,1H3,(H,33,34)/t16-,22-,23-/m1/s1

(5S,8S)-8-[[(1R)-1-[3,5-bis(trifluoromethyl)phenyl]ethoxy]methyl]-8-phenyl-1,9-diazaspiro[4.5]decan-2-one

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Solubility in Formulation 1: ≥ 2.5 mg/mL (5.00 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (5.00 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)